1. Field of the Invention
This invention relates to the field of chain and chain links, especially long, high strength chin for mooring lines and tension legs used to connect offshore platforms to the sea floor. The invention pertains to such chain formed of synthetic materials, especially to a composite that includes plastic resin reinforced with high strength fibers.
2. Description of the Prior Art
Conventional mooring lines and tension legs are made from steel rope or cable having a diameter of five to six inches. In service they carry tensile loads for long periods while submerged in sea water. But the weight of steel in sea water is 92 percent of its weight in air. Therefore, due to the great size, length and weight of conventional steel cables, offshore platforms fixed to the sea floor by such cables must be larger than otherwise required so they can buoy the lines. Use of tubular cables of composite material to reduce weight of mooring lines is described in U.S. Pat. No. 4,589,801.
An articulated riser supporting multiple fluid handling lines extending between a structure on the sea bottom and a surface vessel is described in U.S. Pat. No. 4,031,919. Adjacent segments of the riser are joined mutually by a universal joint, which provides axial force continuity between the riser segments while permitting relative pivotal movement between them.
Various techniques, employed to connect long, flexible lengths of belt, cable and filament, to form longer lengths and endless belts are known. The cable loop connector described in U.S. Pat. No. 4,150,906 releasably joins loops located at the ends of cables. The connector carrying a hook, is fastened to a first cable by sliding a tapered portion of the cable through a tapered opening such that the first cable extends beyond the connector and loops back to engage the hook. The loops of adjacent cables so arranged are looped together to connect the cables.
A spiral seam for joining the ends of a Papermaker's fabric is described in U.S. Pat. No. 4,862,926. Yarn is looped over pintles, which also connect coiled members to the yarn, at adjacent ends of the fabric. The coiled members of each fabric are aligned and interleaved mutually with the coiled members at the end of the adjacent fabric. Then another pintle passes through aligned loops formed in the coils to connect the fabrics.
The free ends of belts are connected to make endless belts by passing a pin or link between loops fixed to the belt ends, as shown in U.S. Pat. No. 2,185,563. Belt ends are connected also by fixing to each belt end a clamp having a loop facing the other free end. A bearing having a transverse hole is located within each clamp. Then links, located at opposite lateral sides of the belt and having axially spaced holes, are arranged so that the holes of the links and bearings are aligned. Finally, pintles are inserted through the holes of the links and bearings to connect the belt ends. A device of this type is described in U.S. Pat. No. 2,675,592.
The enormous length and great size of conventional mooring lines and tension legs makes transport and placement of them difficult. Typically they are transported by rail to a shoreline, fitted with flotation gear and towed to the offshore service site. If their weight and bulk could be reduced substantially and their ability to be lengthened and shortened readily could be improved, then they could be assembled to a predetermined length and towed with minimum flotation support to the offshore site.